Heads up display system

ABSTRACT

A heads up display system of a vehicle including a combiner screen having a first substantially transparent substrate defining a first surface and a second surface, a second substantially transparent substrate defining a third surface and a fourth surface. A primary seal is disposed between the first and second substrates. The seal and the first and second substrates define a cavity therebetween. An electro-optic material is positioned within the cavity and a reflective polarizer is positioned on one of the first and second surfaces. A projector projects light having a first polarization toward the first surface of the first substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 62/205,376, filed on Aug. 14, 2015, entitled“ELECTRO-OPTIC ASSEMBLY,” the entire disclosure of which is herebyincorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to a heads up display, and moreparticularly, to a heads up display having a transflective layer.

BACKGROUND

Heads up displays for vehicles may provide information overlaid onambient light transmitted through the display. In some circumstances,reflectance off of surfaces of the display may produce undesirabledouble imaging.

SUMMARY OF THE DISCLOSURE

According to at least one aspect of the present disclosure, a heads updisplay system of a vehicle includes a combiner screen having a firstsubstantially transparent substrate defining a first surface and asecond surface, a second substantially transparent substrate defining athird surface and a fourth surface. A primary seal is disposed betweenthe first and second substrates. The seal and the first and secondsubstrates define a cavity therebetween. An electro-optic material ispositioned within the cavity and a reflective polarizer is positioned onone of the first and second surfaces. A projector projects light havinga first polarization toward the first surface of the first substrate.

According to another aspect of the present disclosure, a combiner screenfor a heads up display includes at least two substantially transparentsubstrates positioned in a spaced apart configuration. An electro-opticmaterial is positioned between the at least two substantiallytransparent substrates. A reflective polarizer is positioned between theelectro-optic material and at least one of the substrates. The combinerscreen includes an electrically conductive layer. The reflectivepolarizer and the electrically conductive layer are positioned onopposite sides of the electro-optic material.

According to another aspect of the present disclosure, a heads updisplay system of a vehicle, including a projector for projecting lightof a first polarization and a combiner screen. The combiner screenincludes a substantially transparent substrate defining a first surfaceand a second surface. The substrate is curved along at least one axis. Areflective polarizer is positioned on the second surface of thesubstantially transparent substrate. The combiner screen has areflectance of the first polarization of light greater than about 40%.

These and other features, advantages, and objects of the presentdisclosure will be further understood and appreciated by those skilledin the art by reference to the following specification, claims, andappended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1A is a front elevational view of a heads up display system,according to one example;

FIG. 1B is a front elevational view of the heads up display system,according to another example;

FIG. 2A is a cross-sectional view of the combiner screen taken at lineIIA of FIG. 1A, according to one example;

FIG. 2B is a cross-sectional view of the combiner screen taken at lineIIB of FIG. 1A, according to one example;

FIG. 2C is a cross-sectional view of the combiner screen taken at lineIIC of FIG. 1A, according to one example;

FIG. 3A depicts a cross-sectional view of the combiner screen taken atline IIIA of FIG. 1A, according to another example;

FIG. 3B depicts a cross-sectional view of the combiner screen taken atline IIIB of FIG. 1A, according to another example;

FIG. 4A depicts a schematic view of the heads up display system,according to one example; and

FIG. 4B depicts a schematic view of the heads up display system,according to another example.

DETAILED DESCRIPTION

Additional features and advantages of the invention will be set forth inthe detailed description which follows and will be apparent to thoseskilled in the art from the description, or recognized by practicing theinvention as described in the following description, together with theclaims and appended drawings.

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itself,or any combination of two or more of the listed items can be employed.For example, if a composition is described as containing components A,B, and/or C, the composition can contain A alone; B alone; C alone; Aand B in combination; A and C in combination; B and C in combination; orA, B, and C in combination.

In this document, relational terms, such as first and second, top andbottom, and the like, are used solely to distinguish one entity oraction from another entity or action, without necessarily requiring orimplying any actual such relationship or order between such entities oractions. The terms “comprises,” “comprising,” or any other variationthereof, are intended to cover a non-exclusive inclusion, such that aprocess, method, article, or apparatus that comprises a list of elementsdoes not include only those elements but may include other elements notexpressly listed or inherent to such process, method, article, orapparatus. An element preceded by “comprises . . . a” does not, withoutmore constraints, preclude the existence of additional identicalelements in the process, method, article, or apparatus that comprisesthe element.

With regard to FIGS. 1A-2A, reference numeral 10 generally designates aheads up display system of a vehicle 14. The heads up display 10 mayinclude a combiner screen 18. The combiner screen 18 may include a firstsubstantially transparent substrate 22 defining a first surface 22A anda second surface 22B. A second substantially transparent substrate 26defines a third surface 26A and a fourth surface 26B. A primary seal 34is disposed between the first and second substrates 22, 26. The seal 34and the first and second substrates 22, 26 are positioned in a spacedapart configuration to define a cavity 38 therebetween. An electro-opticmaterial 42 is positioned within the cavity 38. A transflective layer 46is positioned on the first surface 22A. A projector 50 projects lighttoward the first surface 22A of the first substrate 22. The light fromthe projector 50 may be unpolarized or polarized. Polarized lightemitted from the projector 50 may have a horizontal or verticalpolarization angle (e.g., a first or second polarization of light), a45° angle polarization or variations therebetween.

With respect to FIGS. 1A and 1B, the heads up display system 10 isdepicted within the vehicle 14. It will be understood that whiledepicted within the vehicle 14, the heads up display system 10 mayequally be used in aerospace applications, window applications,transparency applications, augmented realty applications and otherapplications where a viewer may wish to see both information (e.g.,vehicle related functions or driver assistance systems such as alerts,warnings or vehicle diagnostics) and what is behind the combiner screen18. As an example, in FIGS. 1A and 1B, the speed of the vehicle 14 isbeing displayed on the combiner screen 18 using an image of aspeedometer. Heads up displays are used in many automotive and aerospaceapplications to present information to a driver or pilot while allowingsimultaneous forward vision. In the depicted examples within the vehicle14, the combiner screen 18 may extend from an instrument panel 62 and/orcluster hood 66 (FIG. 1A) or be positioned directly on or integrated aspart of a windscreen 70 of the vehicle 14 (FIG. 1B). In the exampleswhere the combiner screen 18 extends from the instrument panel 62 and/orcluster hood 66, the combiner screen 18 may be a standalone component.Such an example may be advantageous in providing shapes (e.g.,curvature) to the combiner screen 18 which are different than thewindscreen 70. In examples where the combiner screen 18 is located on orwithin the windscreen 70, the combiner screen 18 may share one or moresubstrates (e.g., the first or second substrates 22, 26) with thewindscreen 70. Such an example may be advantageous in reducingcomplexity, weight and manufacturing costs of the heads up displaysystem 10 and the vehicle 14.

The projector 50 is positioned proximate the combiner screen 18 and isconfigured to project light onto the combiner screen 18, as explained ingreater detail below, to form an image which is reflected toward anintended viewer (e.g., a driver or occupant of the vehicle 14). Theprojector 50 may be located proximate the cluster hood 66, or in a roof74 of the vehicle 14. The projector 50 is a light engine capable ofproducing un-polarized or polarized light including, but not limited to,certain liquid crystal displays (LCDs), laser diodes, and organic lightemitting diodes (OLEDs). In polarized light examples of the projector50, the polarized light emitted may have a horizontal or verticalpolarization angle or variations therebetween. In some instances, thepolarized light from the projector 50 may be circularly polarized. Forexample, circular polarization of the light may be achieved whenlinearly polarized light from the projector 50 passes through a ¼ waveplate. The combiner screen 18 of the heads up display system 10 isshaped, as explained in greater detail below, such that a resultantreflected image “appears” to be forward of the combiner screen 18 andforward of the vehicle 14. The exact surface contour of the combinerscreen 18 needed to attain this characteristic is a function ofproperties of the projector 50, location of the combiner screen 18,location of the projector 50 and the location of the viewer (e.g., thedriver and/or passenger to which information is intended to bedisplayed). Having the image projected forward of the vehicle 14 allowsthe viewer to obtain the desired information without having to changethe focal distance of the viewer's eyes. In a traditional displaylocated within the vehicle 14, the viewer's eyes often have to refocusto the shorter viewing distance, thus decreasing the time spent viewingthe road. Furthermore, the viewer's eyes will also then have to re-focuson the road ahead, which further decreases the time spent viewing theroad and forward conditions. The shape of the combiner screen 18 shouldalso be selected so as to preserve the basic characteristics of theprojected image (i.e., straight lines remain straight, aspect ratios ofimages are preserved, etc.).

Although depicted on a driver side of the vehicle 14, it will beunderstood that the heads up display system 10, or components thereof(e.g., the combiner screen 18 and/or the projector 50), may bepositioned on a passenger side of the vehicle 14, or a top of thewindscreen 70, without departing from the teachings provided herein.According to one example, the combiner screen 18 may be located on, orproximate an, upper portion of a windscreen 70. As explained in greaterdetail below, the combiner screen 18 may be operated at differenttransmittance levels to affect a variety of functions. For instance,when ambient light levels at the front of the vehicle 14 are relativelyhigh, the combiner screen 18 may be operated at a darkened state toincrease the visibility of information reflected therefrom. In anotherinstance, the combiner screen 18 may be operated at a darkened state tofunction as a sun visor thereby shielding the eyes of the viewer fromincoming sunlight. Thus, it should be appreciated that the transmittancelevels of the combiner screen 18 may be adjusted independently ofdisplay functionality. That is, the transmittance levels of the combinerscreen 18 are adjustable regardless of whether or not information isbeing displayed or the projector 50 is emitting light. In someinstances, it may be desirable to have more than one combiner screen 18.For example, a first combiner screen 18 may be positioned on the driverside to display information (e.g., vehicle related information) to thedriver and/or function as a sun visor. A second combiner screen 18 maybe positioned on the passenger side to display information (e.g.,vehicle related information and/or media, such as movies and games) tothe passenger and/or function as a sun visor. It is contemplated thatthe various functions of the combiner screen 18 described herein may beautomatically and/or manually controlled. For example, the combinerscreen 18 may be darkened in response to ambient light levels sensed bya vehicle light sensor (e.g., proximate the windscreen 70 or in arearview mirror assembly). According to various examples, the combinerscreen 18 may be configured to fail in a transparent state (i.e.,ambient light may still pass though the combiner screen 18.

Referring now to FIG. 2A, in the depicted example, the combiner screen18 includes the first and second substrates 22, 26. The first substrate22 may be composed of a substantially transparent material such as glass(e.g., soda lime glass), a polymeric material (e.g., acrylic and/orpolycarbonate), or combinations thereof. The first substrate 22 may havea thickness of less than about 2.2 mm, 2.0 mm, 1.5 mm, 1.2 mm or lessthan about 1.0 mm. The first substrate 22 may take a variety of shapesincluding square, rectangular, circular, oblong and combinationsthereof. The first substrate 22 may have a length and/or width dimensionof, or greater than, about 10 mm, 20 mm, 50 mm, 75 mm, 85 mm, 100 mm,150 mm, 175 mm, 200 mm, 250 mm, 300 mm or 500 mm. According to variousexamples, the first substrate 22 may have a curvature across the lengthor width (i.e., a vertical or horizontal axis) of the substrate 22. Forexample, the first substrate 22 may have a radius of curvature (i.e., asmeasured from a theoretical central point of the curvature of the firstsurface 22A) of less than about 2000 mm, 1500 mm, 1300 mm, 1250 mm, 1200mm, 1100 mm, 1000 mm, 900 mm, 800 mm, 700 mm, 600 mm, 500 mm, 400 mm,300 mm, 200 mm or less than about 100 mm. In a specific example, thefirst surface 22A of the first substrate 22 may be about 500 mm. Inspherical curvature examples of the first substrate 22, the radius ofcurvature of the first surface 22A in a vertical direction and ahorizontal direction may be approximately equal (e.g., about 500 mm). Inyet other examples, the first substrate 22 may be curved to have a“free-form” shape (e.g., the curvature along the horizontal and/orvertical directions may vary). The curvature of the first substrate 22may make the first substrate 22 substantially convex or concave towardthe viewer. It will be understood that the first substrate 22 may be“stitched” together from multiple separate components to form a largerfirst substrate 22. It will be understood that the dimensions, thicknessand/or curvature of the separate components of the stitched example ofthe first substrate 22 may be equal or vary between the separatecomponents.

In the depicted example, the first substrate 22 is part of anelectro-optic element 78. The electro-optic element 78 includes thefirst and second substrates 22, 26, the primary seal 34 and theelectro-optic material 42. The second substrate 26 may be composed of asubstantially transparent material such as glass (e.g., soda limeglass), a polymeric material (e.g., acrylic), or combinations thereof.It will be understood that the second substrate 26 may have the same ordifferent dimensions, thicknesses and/or radii of curvature as the firstsubstrate 22. Further, it will be understood that the second substrate26 may be “stitched” together in a similar manner to that described inconnection with the first substrate 22. In a specific example, thesecond substrates 26 may be approximately 1.6 mm in thickness. Thesecond substrate 26 may have a curvature along its length and width,similar to that of the first substrate 22. In a specific example, thesecond substrate 26 may have a spherical radius of curvature ofapproximately 1250 mm. Edges of the first and second substrates 22, 26may be generally rounded. The radius of curvature of the rounded edgesmay be greater than about 2.5 mm.

When laminating two rigid substrates (e.g., the first substrate 22 andthe second substrate 26) it is important that the stress is minimized inthe final lamination. For example, if there are two pieces of bent glassthat are 3 mm in thickness, and the curvature of each piece does notmatch well, the force required to hold the two pieces parallel is high,and, over time, the lamination may fail, especially at elevatedtemperatures often found in automotive and aerospace applications. Onesolution to this stress problem is to make sure the curvature on thesubstrates match very accurately. In a specific example, the first andsecond substrates 22, 26, with all intervening layers as describedbelow, may be curved or bent at an elevated temperature together to forma matched pair so that there is high curvature match between the firstand second substrates 22, 26.

In the depicted embodiment, positioned on the second and third surfaces22B, 26A of the respective first and second substrates 22, 26 is anelectrically conductive layer 86. The electrically conductive layers 86may include a transparent conductor such as a transparent metal oxide(e.g., indium tin oxide, F:SnO2, ZnO, IZO), carbon (graphene and/orgraphite) and/or a conductive metal mesh (e.g., nanowires). In indiumtin oxide examples, the electrically conductive layers 86 may have asheet resistance of approximately 12 ohms/sq.

The first and second substrates 22, 26 can be positioned in a parallelrelationship and sealed around the perimeter using the primary seal 34.The seal 34 extends around the second and third surfaces 22B, 26A toconfine the electro-optic material 42 between the first and secondsubstrates 22, 26. Additional information related to forming a sealbetween a first and second substrate can be found in U.S. Pat. No.5,790,298, entitled “METHOD OF FORMING OPTICALLY TRANSPARENT SEAL ANDSEAL FORMED BY SAID METHOD,” which is herein incorporated by referencein its entirety.

According to one example, the electro-optic element 78 may be a liquidcrystal device, including a liquid crystal medium (e.g., theelectro-optic material 42), configured to attenuate light transmittedthrough the combiner screen 18 (i.e., decrease the transmission of lightthrough the combiner screen 18). In another example, the electro-opticelement 78 may be a suspended particle device. In yet another example,the electro-optic element 78 may be an electrochromic element. In suchan example, the electro-optic material 42 of the electro-optic element78 is an electrochromic medium which includes at least one solvent, atleast one anodic material, and at least one cathodic material.Typically, both of the anodic and cathodic materials are electroactiveand at least one of them is electrochromic. It will be understood thatregardless of its ordinary meaning, the term “electroactive” may mean amaterial that undergoes a modification in its oxidation state uponexposure to a particular electrical potential difference. Additionally,it will be understood that the term “electrochromic” may mean,regardless of its ordinary meaning, a material that exhibits a change inits extinction coefficient at one or more wavelengths upon exposure to aparticular electrical potential difference. Electrochromic components,as described herein, include materials whose color or opacity areaffected by electric current, such that when an electrical current isapplied to the material, the color or opacity changes from a first phaseto a second phase. The electrochromic component may be a single-layer,single-phase component, multi-layer component, or multi-phase component,as described in U.S. Pat. No. 5,928,572 entitled “ELECTROCHROMIC LAYERAND DEVICES COMPRISING SAME,” U.S. Pat. No. 5,998,617 entitled“ELECTROCHROMIC COMPOUNDS,” U.S. Pat. No. 6,020,987 entitled“ELECTROCHROMIC MEDIUM CAPABLE OF PRODUCING A PRE-SELECTED COLOR,” U.S.Pat. No. 6,037,471 entitled “ELECTROCHROMIC COMPOUNDS,” U.S. Pat. No.6,141,137 entitled “ELECTROCHROMIC MEDIA FOR PRODUCING A PRE-SELECTEDCOLOR,” U.S. Pat. No. 6,241,916 entitled “ELECTROCHROMIC SYSTEM,” U.S.Pat. No. 6,193,912 entitled “NEAR INFRARED-ABSORBING ELECTROCHROMICCOMPOUNDS AND DEVICES COMPRISING SAME,” U.S. Pat. No. 6,249,369 entitled“COUPLED ELECTROCHROMIC COMPOUNDS WITH PHOTOSTABLE DICATION OXIDATIONSTATES,” and U.S. Pat. No. 6,137,620 entitled “ELECTROCHROMIC MEDIA WITHCONCENTRATION ENHANCED STABILITY, PROCESS FOR THE PREPARATION THEREOFAND USE IN ELECTROCHROMIC DEVICES;” U.S. Patent Application PublicationNo. 2002/0015214 A1 entitled “ELECTROCHROMIC DEVICE;” and InternationalPatent Application Serial Nos. PCT/US98/05570 entitled “ELECTROCHROMICPOLYMERIC SOLID FILMS, MANUFACTURING ELECTROCHROMIC DEVICES USING SUCHSOLID FILMS, AND PROCESSES FOR MAKING SUCH SOLID FILMS AND DEVICES,”PCT/EP98/03862 entitled “ELECTROCHROMIC POLYMER SYSTEM,” andPCT/US98/05570 entitled “ELECTROCHROMIC POLYMERIC SOLID FILMS,MANUFACTURING ELECTROCHROMIC DEVICES USING SUCH SOLID FILMS, ANDPROCESSES FOR MAKING SUCH SOLID FILMS AND DEVICES,” which are hereinincorporated by reference in their entirety. According to variousexamples, the electro-optic element 78 may be configured to fail in atransparent state such that in the event of failure, the combiner screen18 may still be usable. Use of electro-chromic examples of theelectro-optic element 78 may be advantageous because electrochromics mayhave a very wide gray scale. Further, the gray scale of theelectrochromics may be angle independent such that the perceiveddarkening of the electro-optic element 78 does not vary as a drivershifts their perspective of the combiner screen 18.

Referring now to FIGS. 2A and 2B, the combiner screen 18 may include oneor more transflective layers 46. The transflective layer 46 is a layerwhich may transmit a portion of incident light and reflect a portion ofincident light. According to various examples, the transflective layer46 may be configured to reflect a percentage of light of anypolarization angle, or may be configured to reflect light of only acertain polarization angle. The transflective layer 46 is configured toreflect a primary image from the projector 50 (FIG. 1A) while alsopermitting ambient light to pass through the combiner screen 18. In thedepicted examples, the transflective layer 46 may be positioned on thefirst surface 22A of the first substrate 22 (FIG. 2A) and/or on thesecond surface 22B of the first substrate 22. It will be understood thatthe transflective layer 46 may alternatively be positioned on the thirdor fourth surfaces 26A, 26B without departing from the teachingsprovided herein. The transflective layer 46 and the electricallyconductive layers 86 (e.g., on the third surface 26A) are positioned onopposite sides of the electro-optic material 42.

According to various examples, the transflective layer 46 may includeone or more reflective polarizers. Such reflective polarizers mayinclude films. Use of a reflective polarizer as the transflective layer46 may increase the efficiency of the heads up display system 10. Forexample, a non-polarization sensitive reflector that is 50% reflectivewill reflect 50% of the polarized light while transmitting the rest. Incontrast, when the reflective polarizer is oriented such that itsreflective axis is parallel to the polarization angle of the lightoutputted by the projector 50, approximately 100% of the polarized lightwill be reflected and approximately 50% of ambient light will betransmitted (e.g., due to the random polarization angles of ambientlight). The reflective polarizers may include a wire grid polarizer or amultilayer plastic film such as a dual brightness enhancement film(DBEF) polarizer

In examples of the transflective layer 46 incorporating a DBEF filmreflective polarizer, the reflective polarizer may be laminated directlyto curved examples of the first and/or second substrates 22, 26.Although laminating a film to a flat rigid substrate is known in theart, it has been discovered that lamination of the reflective polarizer,specifically DBEF film examples of the reflective polarizer, to curvedsubstrates may produce an excellent transflective layer 46. Evenfurther, it is surprising and unexpected to find that the DBEF film maybe successfully laminated to a substrate with curvature in twodimensions (e.g., spherically curved). DBEF film examples of thetransflective layer 46 may be laminated to substrates (e.g., the firstand/or second substrates 22, 26) with a curvature having a radius ofgreater than or equal to about 500 mm, 600 mm, 700 mm, 800 mm, 900 mm,1000 mm, 1100 mm, 1200 mm, 1230 mm, 1300 mm, 1400 mm or about 1500 mm inthe vertical and/or horizontal directions. The laminated examples of theDBEF film may have a reflectance of ambient light greater than about 5%,10%, 20%, 30%, 40%, 45%, 49%, 50%, or greater than about 51%. Thelaminated examples of the DBEF film may have a transmittance of ambientlight greater than about 5%, 10%, 20%, 30%, 40%, 45%, 49%, 50%, orgreater than about 51%. Further, the laminated examples of the DBEF filmmay have a reflectance of greater than about 30%, 40%, 50%, 60%, 70%,80%, 90%, 91% 95%, or 99% of light having a polarization anglesubstantially equal to the reflective polarization angle of thereflective polarizer. According to a specific example, a DBEF film ispositioned and laminated between two pieces of soda lime glass with aspherical radius of 500 mm and size of 175 mm×85 mm. The reflectance ofthe laminated example is approximately 51% and the transmission isapproximately 46%. When measured with a crossed absorbing linearpolarizer, the transmission drops to about 1.5%. A similar constructionwith a flat glass substrate produces identical results demonstratingthat with this construction, the reflective polarizer properties havenot changed as a result of laminating to a bent substrate.

Referring now to FIG. 2B, depicted is an alternate example of thecombiner screen 18 of the heads up display 10. In the depicted example,the transflective layer 46 is positioned within the electro-opticelement 78 on the second surface 22B of the first substrate 26. In suchan example, the transflective layer 46 may include a wire gridpolarizer. It will be understood that the transflective layer 46 mayalso be applied to the third surface 26A without departing from theteachings provided herein. In the depicted example, the transflectivelayer 46 functions as one of the electrically conductive layers 86 toprovide electrical power to the electro-optic material 42 of theelectro-optic element 78. In other words, the wire grid polarizerexample of the transflective layer is electrically connected with theelectro-optic material 42.

Use of a wire grid polarizer as the transflective layer 46 in thedepicted configuration (i.e., within the electro-optic element 78) mayoffer several advantages. If the wire grid is conductive, it can be usedas one of the electrically conductive layers 86 for the electro-opticdevice 78 such that the wire grid polarizer will function as both thetransflective layer 46 and the electrode. This example of thetransflective layer 46 may be combined with other coatings to improveconductivity to better function as an electrode. The wire gridpolarizer/electrically conductive layer 86 may be aligned with thepolarization angle of the projector 50 to maximize the reflection of theprimary image.

Referring now to FIGS. 2A and 2B, in regards to examples of the combinerscreen 18 incorporating the electro-optic element 78, the imageprojected onto the combiner screen 18 should be bright enough to see inany condition. This is particularly challenging when the lightingoutside the vehicle 14 is bright. The contrast between the reflectedlight from the combiner screen 18 and the lighting behind the combinerscreen 18 can be low on a bright sunny day. A brighter, more intenselighting source (e.g., projector 50) improves the contrast, increasingthe brightness of reflected image of the combiner screen 18, but may notbe the most economical solution and a reflected image that is brightenough to provide reasonable contrast in very bright daylight conditionsmay be too bright in other conditions. Although controls may be used todeal with variations in brightness, the specific background to thecombiner screen 18 is ever changing when the vehicle 14 is moving, anddepends in part on the position of the driver's eyes. Accordingly, asdescribed above, the electro-optic element 78 can be configured to lowerthe transmission of the combiner screen 18 to increase the contrast ofthe reflected image relation to the background of the combiner screen18.

As explained above, there may be a need for a higher or lowertransmittance in the un-darkened state, different reflectance values foroptimal contrast ratios, and/or broader dynamic range of thetransmittance levels depending on the application. The initial and rangeof reflectance and transmittance properties of the combiner screen 18 isfurther complicated by the capabilities of the projector 50 and itslight output capabilities along with the light transmittance levels forthe windscreen 70 (FIG. 1A). The windscreen 70 will have a direct impacton the contrast ratio and visibility of the combiner screen 18. Thereare a number of factors which affect the transmittance levels of thewindscreen 70. The minimum light transmittance of the windscreen 70 isbased on the regulations of the locality in which the vehicle 14 issold, but higher transmittance levels may be present based on how thevehicle 14 is equipped and marketed. This range of factors creates theneed for solutions which can be adapted to different vehicle andenvironmental conditions. Accordingly, the electro-optic element 78 canbe controlled to vary the amount of light transmission through thecombiner screen 18 based on input from a control circuit. For example,in daylight conditions the combiner screen 18 may be darkened to improvethe contrast ratio and allow for improved visibility of the reflectedimage from the combiner screen 18.

The electro-optic element 78 can have a clear state reflectance ofapproximately 25% and a transmittance of approximately 24%. Theelectro-optic element 78 can have a low end transmittance ofapproximately 10.5% and a low end reflectance of about 15%.Alternatively, in other examples, the high end transmittance may begreater than about 45% or even about 60%. The characteristics of thedevice may also be altered so that the low end transmittance is lessthan about 7.5% or even less than about 5%. In some examples,transmittance levels down to about 2.5% or less may be achievable.Increasing the high-end transmittance may be obtained by the use ofcoatings and materials which have low absorption, as explained above.Lower low-end transmittances may be obtained through the inclusion ofmaterials which have higher absorption. If a wide dynamic range isdesired, then low absorption materials may be used in combination withelectro-optic materials 42 and cell spacing which attain higherabsorbance in the activated state. Those skilled in the art willrecognize that there exists a multitude of combinations of coatings andelectro-optic materials 42, cell spacing and coating conductivity levelswhich can be selected to attain particular device characteristics.

Referring now to FIG. 2C, in the depicted example, the combiner screen18 includes a third substrate 30. The third substrate 30 may define afifth surface 30A and a sixth surface 30B. The third substrate 30 may becomposed of a substantially transparent material such as glass (e.g.,soda lime glass), a polymeric material (e.g., acrylic), or combinationsthereof. The third substrate 30 may have a thickness of less than about2.2 mm, 2.0 mm, 1.5 mm, 1.2 mm, 1.0 mm, 0.8 mm, 0.6 mm, or less thanabout 0.5 mm. The third substrate 30 may take a variety of shapesincluding square, rectangular, circular, oblong and combinationsthereof. The third substrate 30 may have a length and/or width dimensionof, or greater than, about 10 mm, 20 mm, 50 mm, 75 mm, 85 mm, 100 mm,150 mm, 175 mm, 200 mm, 250 mm, 300 mm or 500 mm. According to variousexamples, the third substrate 30 may have a curvature across the lengthor width (i.e., a vertical or horizontal axis) of the substrate 30. Forexample, the third substrate 30 may have a radius of curvature (i.e., asmeasured from a theoretical central point of the curvature of the fifthsurface 30A) of less than about 1300 mm, 1200 mm, 1100 mm, 1000 mm, 900mm, 800 mm, 700 mm, 600 mm, 500 mm, 400 mm, 300 mm, 200 mm or less thanabout 100 mm. In a specific example, the fifth surface 30A of the thirdsubstrate 30 may be about 500 mm. In spherical curvature examples of thethird substrate 30, the radius of curvature of the fifth surface 30A ina vertical direction and a horizontal direction may be approximatelyequal (e.g., about 500 mm). In yet other examples, the third substrate30 may be curved to have a so-called “free-form” shape (e.g., thecurvature along the horizontal and/or vertical directions may vary). Thecurvature of the third substrate 30 may make the third substrate 30substantially convex or concave toward the viewer. It will be understoodthat the third substrate 30 may be “stitched” together from multipleseparate components to form a larger third substrate 30. It will beunderstood that the dimensions, thickness and/or curvature of theseparate components of the stitched example of the third substrate 30may be equal or vary between the separate components.

In a specific example, the first and third substrates 22, 30, with allintervening layers (e.g., the transflective layer 46), may be curved orbent at an elevated temperature together to form a matched pair so thatthere is high curvature match between the first and third substrates 22,30. Another approach to reduce the stress is to make one of thesubstrates (e.g., the third substrate 30) thin. Even if the curvaturedoes not match well, the thinner substrate may have a significantlyreduced strength. The overall stress, therefore, may be reduced. Sincethe strength of a substrate is related to the cube of the thickness,reducing the thickness has a large effect on strength and, therefore, alarge effect on the stress of the substrates and any intervening layers.Further, a thin third substrate 30 may be advantageous for reflectivityreasons, as explained in greater detail below. In the depicted example,the combiner screen 18 includes the transflective layer 46 positionedbehind the third substrate 30 relative to the viewer. In such anexample, it may be advantageous to use a thin example of the thirdsubstrate 30. When the projector 50 (FIG. 1A) is aligned with thetransflective layer 46, there are essentially two reflections. The firstreflection is the primary reflection off of the transflective layer 46.The secondary reflection is the reflection off of the fifth surface 30Aof the third substrate 30. The reflection from the fifth surface 30Awill be just over 4% with glass examples of the third substrate 30,unless an anti-reflective coating is added. For the best reflectedimage, regardless of the intensity of the reflected image, it may bebeneficial to have as small an offset between the position of theprimary and secondary reflections as possible. A thinner third substrate30 reduces the offset between the two images. If an antireflectivecoating is added to the fifth surface 30A of the third substrate 30, thereflection from the fifth surface 30A may be less than about 0.5%, orless than about 0.3%, or less than about 0.2%. Use of the thirdsubstrate 30 may be advantageous in that it may provide protection tothe transflective layer 46 (e.g., from scratches, dirt, water, dust,etc. that may be present in an automotive environment). Further, use ofthe thin examples of the third substrate 30 and the transflective layer46 position between the sixth and first surfaces 30B, 22A may allow forthe reduction or elimination of antireflective layers within thecombiner screen 18.

Referring now to FIGS. 3A and 3B, depicted are examples of the combinerscreen 18 not including the electro-optic element 78. With reference toFIG. 3A, the combiner screen 18 may be formed of a single substrate(e.g., the first substrate 22). In the depicted example, thetransflective layer 46 is positioned on the first surface 22A of thefirst substrate 22. In the depicted example, the first substrate 22 iscurved as described in connection with the example of the combinerscreen 18 disclosed in connection with FIGS. 2A and 2B. As thetransflective layer 46 is exposed to the environment (i.e., not coveredor protected by a substrate), an optional protective layer may bedisposed over the transflective layer 46 to protect it fromenvironmental exposure. Such an example where the combiner screen 18includes the transflective layer 46 on the first surface 22A of thefirst substrate 22 may be advantageous in that it may eliminate anydouble reflection that may be present due to a substrate being presentbetween the transflective layer 46 and the viewer. It will be understoodthat in practice the reflectance off of the first surface 22A may notcreate any significant double image (e.g., the reflectance off of thefirst surface 22A may be about 4% or less) when compared to thereflection off of the transflective layer 46. Since the first surface22A and the second surface 22B may be essentially parallel, the offsetof the two images is generally small and therefore the 4% reflectanceoff of the 1st surface may not create an objectionable double image. Athinner first substrate 22 (e.g., similar to the third substrate 30) mayreduce the offset between the images. A thickness of the first substrate22 less than 1.6 mm may be preferred.

Referring now to FIG. 3B, the transflective layer 46 is depicted aspositioned between the first and second substrates 22, 26. In such anexample, the combiner screen 18 may include one or more concealmentstructures to conceal an edge of the transflective layer 46. Further,the combiner screen 18 may include one or more antireflection coatingspositioned on the first through fourth surfaces 22A-26B.

Referring now to FIGS. 4A and 4B, depicted are examples of the heads updisplay 10 in operation and shown with (FIG. 4B) and without (FIG. 4A) apolarized viewing pane 104 (e.g., polarized sunglasses). To maximize thereflection of the primary image off of the transflective layer 46 of thecombiner screen 18, it is desirable to align the polarization angle ofthe projector 50 to the reflective polarization angle of thetransflective layer 46. Although any polarization angle may be used,there are some considerations for selecting the polarization angle. Inone case (FIG. 4A), the transmission polarization angle of thetransflective layer 46 can be near vertical and the reflectivepolarization angle will be aligned substantially at a horizontal anglewhile the projector 50 emits light having a horizontal anglepolarization. Such a configuration may be advantageous, in that glare(e.g., horizontally polarized light reflected off surfaces) may beprevented from transmission through the combiner screen 18 whilereflecting nearly all of the light from the projector 50. For example,greater than 50%, 60%, 70%, 80%, 90%, or greater than 99% of thepolarized light from the projector 50, may be reflected toward theviewer. In another case (FIG. 4B), the polarization angle of theprojector 50 can be near vertical and the reflective polarization angleof the transflective layer 46 of the combiner screen 18 may also be nearvertical. In this case, the primary image reflected from the projector50 would be easily seen even when wearing polarized sunglasses (e.g.,the polarized viewing pane 104 or other polarized viewing filter) as thetransmission polarization angle of the sunglasses is also vertical. Insuch an example, the combiner screen 18 may appear almost opaque sincethe horizontally polarized light transmitted through the transflectivelayer 46 would be blocked by the sunglasses; the viewer would still beable to view the primary image. It will be understood that in exampleswhere the projector emits horizontally polarized light, use of thepolarized viewing pane 104 may eliminate the reflected image availableto the viewer, but the combiner screen 18 would still appeartransparent. In yet another case, the light emitted from the projector50 and the reflective polarization angle of the transflective layer 46may be oriented at 45 degrees. Such an example may allow some of thelight from the projector 50, and some of the light transmitted throughthe combiner screen 18, to be viewed by the viewer wearing sunglasses.Another configuration that may be advantageous is the use of circularlypolarized light from the projector 50 and a reflective circularpolarizer example of the transflective layer 46. In this configurationthe projector 50 would emit light of the first circular polarization andthe transflective layer 46 would reflect light of the first circularpolarization and transmit light of a second circular polarization. Sincesunglasses (e.g., the polarized viewing pane 104) are typically linearlypolarized, some light of the first circular polarization and some lightof the second circular polarization would be transmitted through thepolarized sunglasses to the viewer. In this configuration the viewercould see both the projected image and the ambient background imageregardless of head orientation while wearing polarized sunglasses.

Use of the present disclosure may offer several advantages. First, useof reflective polarizer examples of the transflective layer 46 allows anincrease in the efficiency of the combiner screen 18. As the reflectivepolarizer both reflects light of one polarization and transmits light ofanother, it is able to increase the contrast of the combiner screen 18simultaneously by reflecting a high percentage of light from theprojector 50 while decreasing the transmittance of light through thecombiner screen 18. Third, the above disclosure allows for the formationof light and cost effective combiner screens 18 for heads up displays.As an electro-optic element 78 is not always needed for the examplesprovided herein, the combiner screen 18 may be as simple to form as atransflective layer 46 on a curved substrate (e.g., the first or secondsubstrates 22, 26). Fourth, the examples of heads up displays 10provided herein may still be functional with the use of polarized sunglasses and polarized viewing panes 104. Fifth, the combiner screen 18may function both to reduce the glare experienced by the viewer, whilealso functioning as a sun shade. Sixth, in examples utilizing areflective polarizer as the transflective layer 46, there may be nosignificant reflection of light from the projector 50 off of surfacesbehind (e.g., relative to the projector 50) the reflective polarizersince little to no display light will make it through. Such an examplemay be advantageous in that it will allow for the reduction orelimination of antireflective coatings on surfaces other than thatbetween the projector 50 and the reflective polarizer. Seventh, use ofelectrochromic examples of the electro-optic element 78 may allow for aclear, or transparent state, failure mode of the electro-optic element78 such that ambient light may still pass through the combiner screen 18even when the electro-optic element 78 has failed (i.e., the combinerscreen 18 may still be used). Further, use of electrochromic examples ofthe electro-optic element 78 may allow for angle independent gray scaleof the combiner screen 18. As such, shifting of the viewing perspectiveof the combiner screen 18 may not affect the perceived level of ambientlight attenuation, or image contrast, of the combiner screen 18.

Modifications of the disclosure will occur to those skilled in the artand to those who make or use the disclosure. Therefore, it is understoodthat the embodiments shown in the drawings and described above aremerely for illustrative purposes and not intended to limit the scope ofthe disclosure, which is defined by the following claims, as interpretedaccording to the principles of patent law, including the doctrine ofequivalents.

It will be understood by one having ordinary skill in the art thatconstruction of the described disclosure, and other components, is notlimited to any specific material. Other exemplary embodiments of thedisclosure disclosed herein may be formed from a wide variety ofmaterials, unless described otherwise herein.

For purposes of this disclosure, the term “coupled” (in all of itsforms: couple, coupling, coupled, etc.) generally means the joining oftwo components (electrical or mechanical) directly or indirectly to oneanother. Such joining may be stationary in nature or movable in nature.Such joining may be achieved with the two components (electrical ormechanical) and any additional intermediate members being integrallyformed as a single unitary body with one another or with the twocomponents. Such joining may be permanent in nature, or may be removableor releasable in nature, unless otherwise stated.

It is also important to note that the construction and arrangement ofthe elements of the disclosure, as shown in the exemplary embodiments,is illustrative only. Although only a few embodiments of the presentinnovations have been described in detail in this disclosure, thoseskilled in the art who review this disclosure will readily appreciatethat many modifications are possible (e.g., variations in sizes,dimensions, structures, shapes and proportions of the various elements,values of parameters, mounting arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter recited. For example,elements shown as integrally formed may be constructed of multipleparts, or elements shown as multiple parts may be integrally formed, theoperation of the interfaces may be reversed or otherwise varied, thelength or width of the structures, and/or members, or connectors, orother elements of the system, may be varied, and the nature or numeralof adjustment positions provided between the elements may be varied. Itshould be noted that the elements and/or assemblies of the system may beconstructed from any of a wide variety of materials that providesufficient strength or durability, in any of a wide variety of colors,textures, and combinations. Accordingly, all such modifications areintended to be included within the scope of the present innovations.Other substitutions, modifications, changes, and omissions may be madein the design, operating conditions, and arrangement of the desired andother exemplary embodiments without departing from the spirit of thepresent innovations.

It will be understood that any described processes, or steps withindescribed processes, may be combined with other disclosed processes orsteps to form structures within the scope of the present disclosure. Theexemplary structures and processes disclosed herein are for illustrativepurposes and are not to be construed as limiting.

It is also to be understood that variations and modifications can bemade on the aforementioned structures and methods without departing fromthe concepts of the present disclosure, and, further, it is to beunderstood that such concepts are intended to be covered by thefollowing claims, unless these claims, by their language, expresslystate otherwise. Further, the claims, as set forth below, areincorporated into and constitute part of this Detailed Description.

What is claimed is:
 1. A heads up display system of a vehicle,comprising: a combiner screen comprising: a first substantiallytransparent substrate defining a first surface and a second surface; asecond substantially transparent substrate defining a third surface anda fourth surface; a primary seal disposed between the first and secondsubstrates, wherein the seal and the first and second substrates definea cavity therebetween; an electro-optic material positioned within thecavity; and a reflective polarizer positioned on one of the first andsecond surfaces, wherein the reflective polarizer comprises a wire gridpolarizer and is positioned on the second surface of the first substrateand is electrically connected to the electro-optic material; and aprojector for projecting light having a first polarization toward thefirst surface of the first substrate.
 2. The heads up display system ofclaim 1, wherein the reflective polarizer is configured to allowtransmission of a second polarized light and to reflect the light havinga first polarization.
 3. The heads up display system of claim 1, whereinthe first substrate has a spherical curvature.
 4. The heads up displaysystem of claim 3, further comprising: a third substrate positionedbetween the first substrate and the projector, wherein the reflectivepolarizer is positioned on the first surface of the first substrate. 5.The heads up display system of claim 1, wherein the combiner screen hasa reflectance to the light from the projector of greater than about 50%.6. A combiner screen for a heads up display, comprising: at least twosubstantially transparent substrates positioned in a spaced apartconfiguration; an electro-optic material positioned between the at leasttwo substantially transparent substrates; a reflective polarizerpositioned between the electro-optic material and at least one of thesubstrates, wherein the reflective polarizer is electrically coupled tothe electro-optic material; and an electrically conductive layer,wherein the reflective polarizer and the electrically conductive layerare positioned on opposite sides of the electro-optic material.
 7. Thecombiner screen of claim 6, wherein the reflective polarizer iselectrically conductive.
 8. The combiner screen of claim 7, wherein thereflective polarizer is a wire grid polarizer.
 9. The combiner screen ofclaim 6, wherein the at least two substantially transparent substratescomprise three substantially transparent substrates.
 10. The combinerscreen of claim 6, wherein the reflective polarizer is configured toreflect vertically polarized light.
 11. A heads up display system of avehicle, comprising: a projector for projecting light of a firstpolarization; and a combiner screen positioned away from a vehiclewindshield comprising: a substantially transparent substrate defining afirst surface and a second surface, wherein the substrate is curvedalong at least two axes; and a reflective polarizer positioned on thesecond surface of the substantially transparent substrate, wherein thecombiner screen has a reflectance of the first polarization of lightgreater than about 40%.
 12. The heads up display system of claim 11,further comprising: an electro-optic element positioned on an oppositeside of the reflective polarizer than the substantially transparentsubstrate.
 13. The heads up display system of claim 12, wherein thesubstrate has a spherical curvature.
 14. The heads up display system ofclaim 13, wherein the substrate has a radius of spherical curvature ofless than or equal to about 1250 mm.
 15. The heads up display system ofclaim 14, wherein the substrate has a radius of spherical curvature ofless than or equal to about 750 mm.
 16. The heads up display system ofclaim 15, wherein the reflective polarizer comprises a dual brightnessenhancement film.
 17. The heads up display system of claim 12, furthercomprising: an electro-optic material in electrical connection with thereflective polarizer.